Store training codes

[horcsinbalint]

It has been requested that we should also store training codes (Képzés kód) for students.
It should be collected during the application, and should be available like other information about the educational programme on the user's profile page, and should probably be available through the export feature on the users page.
We should also include an explanation on how users can find this. (Like in Neptun they should go to Studies > Training data [Tanulmányok > Képzés adatok] and they can find it there. And we should also include an example, like "IK-PROGINF-NBHU" for Computer Science BSc.)